A digital image generally comprises several image pixels, and each image pixel has limited discrete color values. For example, these color values are gray-scale values of red component, green component, and blue component in an RGB (Red-Green-Blue) color space. A plurality of screen pixels that are arranged in an array on a display device are driven according to the digital image, whereby the digital image can be displayed on the display device.
According to traditional sub pixel driving method, one sub pixel is used for displaying a gray-scale value of one color component of the image pixel. In order to improve a resolution of the display device, more image pixels need to be displayed. That is, a quantity of the sub pixels of a display screen should be increased. However, due to restriction of the manufacturing technology, the quantity of the sub pixels of the display screen can hardly be further increased when the quantity of the sub pixels is increased to a certain extent. As a result, the resolution of the display device can hardly be improved further.
Therefore, according to traditional technology, the digital image with a high resolution needs to be displayed on a display panel with a low resolution, and a spatial resolution and a definition of the digital image displayed therein should be ensured at the same time. In order to display the digital image with a high resolution on the display panel with a low resolution, a sub pixel rendering method as shown in FIG. 1 can be used. According to the sub pixel rendering method, three image pixels are compressed into one screen pixel.
According to the example as shown in FIG. 1, a red sub pixel R, a green sub pixel G, and a blue sub pixel B constitute one screen pixel C or D, and three image pixels are displayed by one screen pixel. With respect to six image pixels M−1, M, M+1, N−1, N, and N+1 that are arranged in sequence in a horizontal direction, the screen pixel C corresponds to image pixels M−1, M, and M+1, and the screen pixel D corresponds to image pixels N−1, N, and N+1. During sub pixel rendering procedure, gray-scale values of a red component of M−1, a green component of M, and a blue component of M+1 are respectively loaded on a red sub pixel, a green sub pixel, and a blue sub pixel of the screen pixel C. Similarly, gray-scale values of a red component of N−1, a green component of N, and a blue component of N+1 are respectively loaded on a red sub pixel, a green sub pixel, and a blue sub pixel of the screen pixel D. In this manner, three image pixels can be displayed by one screen pixel, whereby an apparent resolution of the display device can be improved. However, since a color of the digital image in a contour region or a small region with white color thereof changes rapidly, a serious “colored edge” phenomenon would occur when the image is processed by the sub pixel rendering method.
Therefore, a sub pixel multiplexing method whereby a high resolution of the display device can be ensured, and the “colored edge” phenomenon can be eliminated is needed.